Abstract: This paper evaluates the strategy for controlling ‘unwanted’ immigration that has been implemented by the US government since 1993, and suggests explanations for the failure of that strategy to achieve its stated objectives thus far. Available evidence suggests that a strategy of immigration control that overwhelmingly emphasises border enforcement and short-changes interior (especially workplace) enforcement has caused illegal entries to be redistributed along the south-west border. The evidence also suggests that the financial cost of illegal entry has more than quadrupled; that undocumented migrants are staying longer in the United States; that migrant deaths resulting from clandestine border crossings have risen sharply; and that there has been a surge in anti-immigration vigilante activity. Consequences predicted by advocates of the concentrated border enforcement strategy have not yet materialised: there is no evidence that unauthorised migration is being deterred at the point of origin; that would-be illegal entrants are being discouraged at the border after multiple apprehensions by the Border Patrol and returning home; that their employment prospects in the US have been curtailed; or that the resident population of undocumented immigrants is shrinking. It is argued that a severely constrained employer-sanctions enforcement effort that has left demand for unauthorised immigrant labour intact is the fundamental reason why steadily escalating spending on border enforcement during the last ten years has had such a weak deterrent effect. Reasons for the persistence of a failed immigration control policy are discussed, and alternatives to the current policy are evaluated.